{% macro book_card(book) %}
    <div class="card">
        <a href="/book/{{ book.id }}">
            <img src="{{ book.image }}" alt="{{ book.title }}">
            <h3>{{ book.title }}</h3>
            <div class="tags">
                {% for tag in book.tags %}
                    <span class="tag">{{ tag }}</span>
                {% endfor %}
            </div>
        </a>
    </div>
{% endmacro %}
修改说明：

{% macro search_form(search_query='') %}
    <form method="GET" action="/search" class="search-form">
        <input type="text" name="q" placeholder="有什么想问书娘的吗~~" value="{{ search_query }}">
        <button type="submit" class="btn">搜索</button>
    </form>
{% endmacro %}
